In 3G cellular communication architectures, data services are provided to subscribers using the General Packet Radio Service (GPRS). A GPRS core network routes data between a UMTS Terrestrial Radio Access Network, UTRAN, to which a client (User Equipment or UE) is attached and an IP backbone of the network operator. A so-called GPRS Gateway Support Node (GGSN) provides an interconnection between the GPRS core network and the IP backbone. The IP backbone provides client access to “internal” packet services of the network operator as well as access to the Internet and the various “external” services available over the Internet. The interface between the GGSN and the IP backbone is referred to in the relevant standards as the Gi interface. In the case of SAE/LTE network architectures, that is the so-called 4G networks, the Packet Data Network Gateway (PDN Gateway) within the Evolved Packet Core (EPC) network performs a role broadly similar to that of the GGSN, connecting the EPC to the operator's IP backbone.
Network operators are currently experiencing rapid growth in demand for data services, due in large part to the growing use of streaming media services. These services tend to be centralised “above” the GGSN/PDN Gateway anchor point in the sense that subscribers connect to common servers (hosting the services) regardless of geographical location. In order to reduce the burden placed on networks by this increased demand, it is desirable to allow for the local breakout of data connections such that data traffic does not have to flow unnecessarily through mobility tunnels, e.g. via a subscriber's home network to a visited network. It is further desirable to introduce where possible local data sources, i.e. local streaming servers and local caching, to reduce the path length between data source and subscriber.
FIG. 1 illustrates schematically an example streaming media architecture with deployed caches used to offload the central server. The caches may be located within the Internet, within the IP backbone network, and/or within the operator's network. Considering the latter, in the case of a 3G network, caches could be located within the GPRS core network, for example co-located with or connected to the GGSN, or could be located within the RAN, for example co-located or connected to the Radio Network Controller (RNC). Similarly, in the case of a 4G network, caches may be located in the packet core network (co-located with or coupled to the PDN Gateway) or within the radio access network (co-located with or coupled to the enhanced Node B (eNB)).
Caching data beneath the GGSN/PDN Gateway attachment point, whilst efficient in terms of reducing network traffic, does raise issues regarding subscriber mobility. Subscriber mobility is a requirement for the introduction and acceptance of any data traffic handling solution. Operators and subscribers will not accept a solution which results in the loss of service connections when a subscriber moves from one location to another or is otherwise handed over between network access points. There is an inherent conflict between moving the cache as close as possible to the subscriber equipment in order to reduce network traffic on the one hand, and facilitating subscriber mobility on the other.